Blighted!

Fortunately not our garden, but it has been pretty discouraging for the friends whose garden it is. Buxus blight on the rampage.

I am not the world’s greatest fan of buxus hedging. But I have some sympathy for the multitude of gardeners who are watching their prized box hedges turn brown. Judging by the Google search terms, it is an alarmingly common problem at the moment. “My buxus has no leaves. Is it dead?” Basically, yes. Buxus is an evergreen plant which never loses all its leaves. “Buxus turning brown.” It is dying. If it is any consolation, Prince Charles is reportedly having the same problem at Highgrove.

The problem is buxus blight – cylindrocladium. It is a fungus so it spreads by spore and it has dispersed extensively across the globe. It is particularly troublesome because it is not affected by temperature – hot or cold, its progress is undeterred, particularly in wet or humid conditions. I have yet to see any information on how far the spore can be carried by wind but it is more likely to be kilometres rather than metres. So unless you are in the country, isolated from other buxus, odds on that your buxus will become infected sooner or later, if it isn’t already. You will know if you have it. The leaves turn brown and fall off and it can spread rapidly. Left to follow its natural course, it is generally terminal.

You can treat buxus blight but you don’t seem to be able to eradicate it. This means you will have to continue treating it for the life of the plants. The best you can hope is to hold it at bay because the spore can survive for a year, maybe two, on the dead leaves and I defy anybody to succeed in removing every single blighted leaf.

A blight upon your buxus

If you are going to try and salvage your existing buxus, first up you need to thin and clean out the accumulated debris. I am well aware that this is easier said than done, especially when you have a mature hedge which has become so dense you can almost sit on it. A blower vac is pretty much the one only way to go with blasting out the debris, which must then be removed. And thinning is a painstaking task with secateurs. What you are trying to do is to enable the leaves to shed water as quickly as possible and to allow more air movement. These techniques may slow the spread but they won’t treat the existing condition. You will have to spray. It is a fungus, so you need an anti fungal spray. I don’t know of any specific sprays developed to target this condition, but any of the broad spectrum fungicides might work. Anecdotally, I am told that copper works but I am guessing that you have to get it in the early stages for copper and you may have to spray more frequently.

The bottom line is whether you are willing to commit to repeated spraying to save your buxus hedge. For us, the unequivocal answer is no. We just think it is really bad environmental practice. There is evidence that repeated use of copper is not good for the soils. Amongst other things, it kills earth worms which leads to soil compaction and copper residue is cumulative over time. An occasional application is fine, but committing to ongoing spraying is different. Besides, the whole thing about buxus was that it required minimal maintenance – a clip twice a year kept it in shape. Would you choose it knowing that it requires frequent spraying just to keep it alive?

Suffruticosa (the very low growing baby one) appears to be the worst hit, probably because it is the densest grower. Sempervirens is also badly affected and that is by far the most common form around. Be wary of advice that the Asian forms from Japan and Korea don’t get blight. They are Buxus microphylla and microphylla var. koreana or Buxus sinica. Being larger leaved and a little more open in growth, they may shed the water more quickly and be less affected but overseas research says that no buxus species are immune.

It should be pretty obvious at this point that there is no point whatever in taking out affected plants and replacing them with fresh ones of the same variety. The problem is not the individual plants – it is the fungal spores swirling around.

As if the news of buxus blight is not bad enough, there is a further quandary when it comes to a substitute. Put simply, there is no like for like swap. Space does not allow me to look at the alternatives here, but if you want to know more, you will find some options on Buxus Alternatives for Garden Hedges. The bottom line is that there is no other single option which is cheap to buy, grows in sun and shade, has good dark green colour, will re-sprout from bare wood and only requires clipping once or twice a year. Personally, I think it is an opportunity to stand back and rethink garden designs which have leaned far too heavily on defining form by endless box hedging and I will return to this theme in the future.

If you haven’t got buxus blight, be grateful and be vigilant.

(first published in the Waikato Times and reproduced here with their permission)